PHENOTYPIC CHARACTERIZATION OF STREPTOCOCCUS-DYSGALACTIAE ISOLATES FROM BOVINE MASTITIS BY THEIR BINDING TO HOST DERIVED PROTEINS

The binding of 80 Streptococcus dysgalactiae mastitis isolates from 51 farms to plasma and connective tissue proteins fibronectin (29 kDa N- terminal fragment), vitronectin, collagen type I, fibrinogen, cu,-macr oglobulin, IgG, and albumin was studied. All isolates bound the bovine 29 kDa fibronectin fragment and the binding of bovine fibrinogen, cap rine albumin, bovine cr,-macroglobulin-trypsin complexes and caprine I gG was also very frequent (92.5, 92.5, 72.5% and 87.5%, respectively). Binding to human vitronectin was observed in 55% of the isolates, whe reas only 20% of the isolates bound human type I collagen. None of the isolates bound native cr,-macroglobulin. Nearly all isolates (91%) bo und more than 3 ligands. The bacterial binding sites for these protein s (termed here receptors) occurred in different combinations of which the combination fibronectin-, albumin-, fibrinogen-, vitronectin-, alp ha(2)-macroglobulin-and IgG-receptor was the most common. More than on e isolate was obtained from 10 farms, The isolates from 5 farms showed close similarity of binding profiles within the farm, indicating that they were of similar origin and suggesting that the binding character istics were relatively stable. Wider variation among the isolates obta ined from other 5 farms was detected. The different isolates of the sa me farm origin varied mostly in the binding of albumin, IgG and fibrin ogen. Interestingly, a difference in the number of receptors between i solates from two different sampling areas was observed. The binding pr ofiles offer a new phenotypic method for epidemiological studies and m ay also when combined with genetical studies provide more insight both into the role of the bacterial plasma and connective tissue protein r eceptors in the infection process and the regulation of receptor expre ssion.